جستجوی مقالات مرتبط با کلیدواژه « Semi » در نشریات گروه « زراعت »

The effect of fire on vegetation of semi-arid steppe has not been studied extensively. Wildfires are rare in some steppe rangelands because of high levels of large herbivore grazing. However, grazing is sometimes restricted or excluded in areas such as national parks or the areas where afforestation projects are conducted. Therefore, sometimes, wildfires occur during the dormant season when litter (the uppermost layer of organic debris on the soil surface; essentially the freshly fallen or slightly decomposed vegetal material) mass has resulted in peak levels. Our study assessed the effects of a single fire on litter mass, forage production, and forage crude protein, Neutral Detergent Fiber (NDF), and Acid Detergent Fiber (ADF) in high altitude rangelands of Eastern Anatolia. We found significant effects of treatment (fire and no fire), years, and sampling date on all variables. Following the prescribed fire in 2011, litter mass and forage production was less in treated plots compared to untreated control plots during both years. The effect of the fire on litter and forage production was more pronounced in 2012 compared to 2013. The effects of the fire on forage quality variables were also greater in 2012 than in 2013. Forage crude protein levels were consistently higher in treated plots during all 2012 sampling periods. Similarly, NDF and ADF tended to be lower in treated plots relative to the control plots during 2012. All effects we found were more pronounced in the first growing season following the fire compared to the second growing season, suggesting a relatively transient nature of fire effects in the steppe vegetation we studied.

A long-term field experiment was conducted for 7 years to evaluate the effect of different amendments to mitigate the adverse effect of saline-sodic water in a calcareous soil under cotton-wheat cropping system. The pooled results over 7 years revealed that the application of saline-sodic water decreased the mean cotton-seed yield by 20.7% as compared to good quality canal water. However, wheat-grain yield was not adversely affected by quality of irrigation water. Among the different amendments, gypsum and farmyard manure were more effective in mitigating the adverse effect of saline-sodic irrigation water. Cotton-seed yield reduction was 9.8% with the addition of farmyard manure and remained only 8.8% with the addition of gypsum as compared to good quality water. However, when saline-sodic water was used alternately with good quality canal water, the recorded cotton-seed yield reduction was only 6.1%. These results suggest that in calcareous soils, farmyard manure is useful in ameliorating long-term deleterious effects of saline sodic irrigation water and sustaining the productivity of cotton-wheat system.

Semi-rigid aluminum containers are being used widely in food industries. They have wrinkle shaped walls for strengthening their physical structure. The objective of this study was to assess the effect of wrinkled parts on the heat transfer and temperature distribution of the containers by Computational Fluid Dynamics (CFD) analysis. Therefore, a precise designed geometry of the wrinkled walls container was compared to a straight one. The analysis was carried out based on the physical properties of a carrot-orange soup. The velocity vectors showed a strong circulation towards the core. The Slowest Heating Zone (SHZ) locations were the same for wrinkled and simplified containers. Average temperature of the symmetric plane and the coldest point of SHZ showed less than 1% difference. The lethality imposed to the SHZ in the wrinkled wall container was about 0.4% more than the straight one. The simulation results revealed that wrinkled walls do not play an important role in increasing heat transfer and as a result, such geometries could be simplified while modeling.

The objective of this research was to investigate the effects of deficit irrigation on physiological and agronomic terms of eggplant to maximize the Water Use Efficiency (WUE) without affecting the final yield and fruit quality parameters under arid environment. Therefore, two field experiments were conducted at two different sites: Ghor Al-Safi, Jordan Valley and Sail Al-Karak, Karak Valley, Karak Province, Jordan, using a common eggplant cultivar (Classic) using five irrigation levels: 20, 40, 60, 80, and 100% based on field capacity. The most stressful Deficit Irrigation (DI) treatments (40 and 20%) resulted in significant effects on leaf area, leaf relative water content, leaf water potential and leaf mineral content. Biochemical parameters also showed an increase in proline and a decrease in chlorophyll content under water deficit conditions. Fruit weight and total yield decreased with DI. The control (100% irrigation treatment) plants revealed higher nutrient contents than the water-stressed plants. The fruit TSS and titratable acidity were increased at both sites as the irrigation regime decreased from 100 to 20%. Fruit nutrient content decreased with increasing water deficit. However, the differences were not significant between the control (100% irrigation treatment) and the 80% irrigation treatment. The 80% treatment showed high water use efficiency with relatively small effects on plant growth performance compared with the control. As a result, DI level at 80% can be utilized to increase WUE without a significant effect on crop growth performance.

Soil erosion by water is the main factor of land degradation, particularly in semi-arid regions where soil productivity is usually low and lowering soil quality can severely decrease crops yields. This study was done in an area of 900 km2 in the semi-arid agricultural region of Hashtroud in northwestern Iran to determine the relationship between soil productivity and soil erodibility. Wheat grain yield (WGY) and soil erodibility factor (K) were measured separately at 108 plots in 36 dry-farming lands under natural rainfall conditions for a two-year period from March 2005 to March 2007. Based on the results, significant differences were observed among the lands in WGY (P< 0.001) and K (P< 0.001). These differences were attributed to variations of soil properties among the lands. There was a negative relationship between WGY and K (R2= 0.77). Multiple regression analysis indicated that both WGY and K were significantly related to aggregate stability and infiltration rate, with a determination coefficient (R2) of 0.74 and 0.90, respectively. Organic matter and calcium carbonate equivalent were the most effective soil properties that enhanced both aggregate stability and infiltration rate. The study revealed that soils with a lower percentage of water-stable aggregates and a lower infiltration rate also tended to have a higher susceptibility to erosion and a lower potential for crop production.

A two-year field experiment was carried out in semi-arid region of southern Iran (Shiraz), during 2007-2008 and 2009-2010 growing seasons using various mixtures of an early- (cv Falat) and a middle-ripening (cv Shiraz) winter wheat cultivar to evaluate the beneficial effects of inducing temporal growth heterogeneity on reduction of intra-specific competition during post-anthesis moisture stress conditions. Treatments were composed of five combination ratios of the two cultivars (1:0; 2:1; 1:1; 1:2, 0:1), and two levels of post-anthesis moisture conditions i.e. equal to Field Capacity and 50% FC. The results showed that the equal ratio (1:1 mixed cropping of early and middle-ripening cultivars) was superior in grain yield components as well as post-anthesis water use efficiency (PWUE) among the mixture treatments. It appeared that mixed cropping of early- and middle-ripening cultivars had the potential for altering the intensified competition under deficient moisture conditions and may improve PWUE. Additional research for determining the best choices of cultivars, mixing ratios, sowing date, phenological differences, input requirements, and management practices for each regional environment are essential to achieve the maximum benefits.

Defoliation produced by abiotic factors and the subsequent re-growth can reduce sugar beet (Beta vulgaris L.) sucrose content and final sugar yield. Field experiments were conducted during 2003 and 2004 growing seasons in the farm of Hellenic Sugar Industry SA, Larissa factory, central Greece. Three sugar beet cultivars (Rival, Europa and Corsica) were ordinary irrigated till the beginning of July and then left without irrigation for a month. Three defoliation levels (control-C, moderate-MD and severe-SD) were performed at early August and irrigation was simultaneously started to promote re-growth. Four samplings were conducted (before defoliation, 15, 30 and 40 days after defoliation) to determine the changes in physiological and productive traits. Yields were lower in 2003 compared to 2004 because sugar beets were grown under more stressful conditions due to the delayed sowing, the higher temperatures and the lower rainfall. Both defoliation level and cultivar had significant effects on physiological and productive traits after re-growth only in 2003. The late-season cultivar, Corsica, showed better LAI maintenance compared to Europa and Corsica and had the greatest performance after re-growth in regard to fresh root weight and sugar yield. Also, this cultivar showed the least decrease of sucrose percentage in fresh root weight and juice purity mainly due to the stable potassium (K) concentration and limited increase of sodium (Na) accumulation in roots. Corsica consumed the least root α-amino N for its re-growth. Quantitative and qualitative traits were negatively affected only by the SD treatment. Plants suffered from MD treatment gradually recovered during growing season. This study demonstrates that under Mediterranean conditions, the adverse effects of re-growth on sugar beet yield and quality depend on the growing conditions and they can be restricted by the selection of an appropriate cultivar.